ideal spreader attachment

[brm3]

I have a mast that needs a set of spreaders and would like opinions on the best way to mount them. Thanks

[Robbie.g]

Something like this is pretty close.

Strong, looks good, straightforward fabrication, whats not to like?
IMHO...Cheers

[brm3]

looks nice. can do thanks

[brm3]

quick question . how does this design relieve stress on side compression of the mast?
thanks

[Douglas]

Ahoy bm , my Forespar mast fabricated around 1985 has spreader bases welded right to the mast wall .

FWIW , author Nigel Calder says this , in his second edition of Boatowner's Mechanical and Electrical Manual ,,,, page 484 , " ......... any welds around the spar produce a week section prone to buckling. Notable in this respect are welded spreader sockets, especially where the sockets wrap a good way around the spar. "

As for mast wall compression at the spreader bases , are you thinking about Z spar's through bar spreader base system ?

[brm3]

yep. you got it. I've seen the bars and the sleeved bolt option. My mast is oval so compression tubes would be challenging. I'm trying to either copy a solid design or come up with something to fit the bill. My wall thickness is 3/16" but I want to be safe with the loading at the point of compression on the wall.
Thanks

[Jim Fulton]

I would expect that a rigid connection between the spreader and the mast like that pictured would increase the likelihood of metal fatigue at the joint due to vibration. All of the spreader bases that I have seen (or paid attention to) have some allowance for the spreader to move, at least a little. Am I off base here?

[brm3]

I guess it would depend on the amount of deflection resulting in flex inducing fatigue. I'm still curious if the side compression of the mast is really a problem. Nigels book raises concern. Is this opinion or fact? Does anyone know? I know how stories can be mutated to unreasonable point.
Thanks

[Robbie.g]

The load is spread over a large area, and using a band has made the spreader load land on double the thickness of material and more than quadruple the spreader cross section surface area.
Spreaders should not move, any movement would in itself, cause fatigue and wear. Many carbon rigs have the mast and spreaders etc glued n glassed. No movement there.

Possibly the 'deflection resulting in flex inducing fatigue' in you post, is an opinion from a bygone day.
Regards

[Ian McColgin]

Since many boats of "a by-gone day" are still sailing, any look at flex or not should start with understanding the engineering of the boat and rig. One might also recall that while there are times when you might get away with a rigid spreader to mast attachment, there are very very few (if any) times when an intelligently engineered flexable connection will do anything but good.

G'luck